Some updates / Scans require windows to be restarted.
If your upgrading versions its also normal for it to request a restart.
If you can tell us as above "What Version" you are using.
And how many restarts you have had to do.
Updates can be configured between 1 day and 1 hr depending upon your settings. So a updated every hour asking you to restart can be a pain in the backside. How ever if you have not restarted it will keep prompting you as a restart is required to settle in the new updates.
Hope that helps
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